A man who began raping his daughter when she was aged three has been jailed for a string of sexual crimes spanning 14 years.

The man, who was granted name suppression to protect his victims, was sentenced to a minimum of seven years preventive detention at the High Court in Auckland on Wednesday for the crimes, which took place between 1979 and 1993 against several children.

He was sentenced on 24 charges - 10 of sexual violation by raping a child under the age of 12, four for unlawful sexual connection with a child under 12, six of indecent assault of a child under 12 and four of inducing an indecent act on a child under the age of 12.

Justice Peter Woodhouse labelled the man's crimes "monstrous" while he sat crying in the dock.

The man is currently in prison, serving the last of a 10-year minimum sentence for sexual offending against children between 1999 and 2002. The children - two step-daughters and a child in his wife's care were aged between three and nine.

The crimes he was sentenced on this week began in 1979 when he raped his three-year-old niece on the floor of her parents' bedroom. His offending against her continued for nine years.

In 1986 he started raping his daughter - aged three - and stopped only when he was jailed in 1989 for sexual offending against other children. He started raping her again in 1991 - the same day he was released from prison.

The man raped his daughter at least once a week until 1993 when she left his care.

"She should never have been there in the first place," Justice Woodhouse said.

The man's crimes came to light earlier this year when his daughter watched a TV programme in which older women confessed they had been raped as children and thought, "if they can do it, I can do it".

But the repeated rapes had already "destroyed her childhood", the court heard.

"Your daughter said she is haunted with deeply ingrained memories. She was suicidal in her teen years and planned her own death so as not to torment herself with the memory of your actions," Justice Woodhouse said.

"She said living as a rape victim makes you feel like you're dying inside. She called your actions monstrous - and that's what they are."

The man admitted the crimes against his daughter earlier this year and when charged, confessed he had also raped his niece. He also raped two other nieces - one who would not come forward, and one who could not be found.

Justice Woodhouse said preventative detention was necessary in order to "send a strong message to the parole board" and the "need to protect the community" from him.